Abstract: Compared with traditional concept, event as a knowledge unit has numerous advantages in terms of knowledge representation. An event consists of a variety of elements including action, object, time, place and etc. But the complexity of event structure brings about difficulties on formalization and inference on events. Due to the lack of effective methods of representation and reasoning for the event elements in text, and the deficiencies of traditional description logic expression on event knowledge, an event element projection is proposed as a new formalization method. By means of powerful expression of extended description logic sublanguage, SROIQ, and based on a new event ontology model, this method has many advantages. Event element projection unifies representation of events and event states, and builds the semantic relations between events and elements. Based on SROIQ, event element projection is able to effectively represent event class, event instances and event elements in all areas and abstract the universal elemental features of events or event relations, and contributes to the construction of domain event ontology and reasoning on event elements. An example of formalization on water pollution emergencies ontology is provided based on SROIQ and element projection method. The general process and steps of event ontology formalization are proposed as well. The semantics of event relations based on element projection and reasoning on event relations are also discussed at last. Event element projection makes element inference compatible with event class inference, simplifies syntax of formalization framework, and enriches the semantic definitions of various event relations. Based on this method and SROIQ, the expression of formalization framework could be enhanced and the reasoning ability could be ensured.